UWB: the new frontier in location

uwb-localizzazione
UWB is an item tracking technology that is coming back into the news. Let’s go into the subject together.

UWB systems are featured in the latest iPhone release (version 11) and car manufacturers are defining the UWB standards to be used for future generations of vehicles.

There are already solutions dedicated to logistics and tracking and tracing on the market.

“It is possible to imagine applications for this technology in different areas: in the museum environment, for example, Nexsoft is carrying out research activities for the location of visitors within a museum facility.”

RTLS Systems

Real-Time Locating Systems (RTLS) are automatic systems that make it possible to identify and track the position of people and objects in real time. They can therefore be used in different contexts:

  • industrial: making factories intelligent through item tracking in complex production processes.
  • logistics: location of goods, semi-finished products, fork-lifts and pallets
  • healthcare: location of patients and medical equipment (e.g. defibrillators that need to be available quickly) within hospital facilities
  • physical security: location of people for access to restricted facilities
  • kid trackers: location of children within defined areas
  • sporting: checking athletes’ performance by tracking their movements
  • museums: location of visitors to provide contextual services.

Indoor and outdoor location

The choice of location technology depends on the context in which it is to operate. The first division is between outdoor and indoor environments. Outdoor location mostly exploits GPS technology and a combination of additional technologies such as phone cells, WiFi networks and lately photographic recognition of places. Location based on GPS alone allows an accuracy of about 10 m, but combined with additional technology and using GNSS Augmentation systems it is possible to improve accuracy to below 5 m.

GPS is a 1973 US project that became operational from 1994 and is the first example of large-scale item tracking. Apart from the limits of precision that make it inapplicable in various areas, it can only be used in outdoor environments. From the 90s, studies began to extend location not only to outdoor areas but also inside buildings.

One difference is immediately clear: GPS tracking provides “absolute” position data (latitude, longitude, altitude) that will be unique worldwide. Indoor location, on the other hand, will provide a “relative” position only valid in the context in which it is placed. Making a comparison with network theory, GPS location provides data comparable to the public address, i.e. unique and reachable from any network node in the world; indoor location, on the other hand, provides a value comparable to that of the private address, i.e. valid only within the local network.

But just as in traditional networks it is possible to make private addresses available to all the world’s nodes, so later systems can insert the relative position of the outdoor element in an “absolute” context.

To give a example: imagining an underground car park whose latitude, longitude and height are known, it is possible to trace the positions of the vehicles in the stalls in terms of absolute position, superimposing indoor location techniques on the georeferencing of the building.

Indoor location technology

Indoor location technologies can make use of acoustic, optical or radio frequency systems.

With regard to radiofrequency it is possible to work both on continuous wave (WLAN and RFID technologies are part of this family) and with pulse signals.

Continuous wave techniques suffer from low precision because they are influenced by multipath fading phenomena.

Multipath fading is a form of distortion in the reception of a signal that causes the addition of time-shifted replicas of the signal arriving at the receiving station overlapping those of the base signal.
Secondary sources are generated by the various paths (multipath) that the signal itself may have followed during its propagation. Furthermore, since the secondary sources follow a different path both from each other and from the primary source (paths characterised by reflections and refractions from different surfaces), the receiving station will receive the signals coming from the various secondary sources attenuated differently from those coming from the primary source.

Since for such systems location is associated with the characteristic of the received signal(s), a distortion of the received signal(s) results in the received information no longer being identifiable.

Case study

In recent years, Nexsoft has designed and implemented a location system based on WiFi technologies in the industrial environment.

The purpose of the system is to locate semi-finished products on the assembly line of a major radar system manufacturer.

During the implementation phase, the location system underwent sensitive multipath fading phenomena due to the movement of huge metal panels.

In such a situation it is necessary to install radio displacement sensing systems to compensate for location errors due to multipath fading.

The location system thus becomes very complex and expensive, which makes it impractical in several areas of application.

UWB location

UWB (Ultra-Wideband) is part of the family of radio frequency technologies characterised by pulsed signals.

UWB is a transmission technique that allows transmission and reception of pulsed radio frequency energy signals.

Thanks to its characteristics it overcomes the problems of other location systems and allows an accuracy of 20 cm in the plane and 30 cm in the space, compared to the accuracy of the order of 5 metres of other indoor location systems.

Compared to other wireless communication technologies this is the one with the highest bandwidth.

tecnologie wireless

UWB localization is characterised by n fixed antennas of known position that allow the location of a mobile object (tag). Both the antennas and the tag can transmit and receive at the same time, so the mobile tag to be located can be both the receiving element of the signal and the source of transmission.

1

In the first example it is the antennas that transmit the signal, the mobile receiving tag processes the received signals and identifies its position as shown in the figure below.

tag UWB
2

In the first example it is the antennas that transmit the signal, the mobile receiving tag processes the received signals and identifies its position as shown in the figure below.

Of the two examples, the second is to be preferred because it shifts both the computational capacity and the transmission of data to fixed and mains-powered equipment. This allows both to reduce the cost of mobile tags and to limit the consumption of the tag’s battery. To reduce the consumption of the mobile tag, further strategies are possible, such as activating transmission by the tag only in the presence of movement.

Now let us look in detail at the case where it is the tag that transmits the signal and the fixed antennas that receive it.

The mobile unit transmits pulsed signals characterised by spherical waves. With four receiving antennas in the space it is theoretically possible to uniquely identify a position.

Clearly, in order for this to happen, it is first necessary to define a reference system and then perform a setup of the environment, associating the signals received from the transmitters to a set of points and then completing the entire mapping of the area by interpolating the set of measured points. RTLS systems use multiple location techniques based essentially on signal arrival times or their power, and UWB uses location techniques based on multilateration.

Multilateration is based on the difference in arrival time (TDOATime Difference Of Arrival) of a signal emitted by a mobile tag to a number of receiving stations (Anchors) located in a known area. Since there is a direct relationship between the arrival time and the distance travelled (Time = Distance / Speed) it is easy to calculate the travel time of the emitted signal. Considering that the signal is travelling in air, one can assume with good approximation the speed of light (c) as the speed of the signal.

TDoA communication process

Receiving stations are separated into one master station and at least two slave stations. The function of the master station is twofold: on the one hand it is a receiving station like the others, on the other hand it sends a synchronisation signal to the slave stations. In the communication process the mobile tag sends a polling message. The receiving stations receive it and record the time of arrival.

Processo comunicazione TDoA

How the TDoA is calculated

AP0:Records the arrival time of the message in the variable T0

AP1:Records the arrival time of the message in the variable T1

AP2:Records the arrival time of the message in the variable T2

AP3:Records the arrival time of the message in the variable T3

 

AP0, AP1, AP2, … APn are the receiving stations. The system clocks of AP0, AP1, AP2, AP3 … APn are synchronised.

Considering the case with four receiving stations, and defining the position of AP0 as the origin of the reference system, we will have the following coordinates:

AP0 (master) : (0,0,0)

AP1 (slave) : (X1,Y1,Z1)

AP2 (slave) : (X2,Y2,Z2)

AP3 (slave) : (X3,Y3,Z3)

Since the speed at which the signal moves is that of light c, the distance to the mobile tag with coordinates (x,y,z) in space will be as follows:

And so the differences between the arrival times are:

calcolo TdOA

When the three functions DT1, DT2 and DT3 are plotted in space, they identify three spherical hyperbolas, and from the intersections of the three hyperbolas we find the position of the tag.

For this method to work properly, all receiving stations must be kept synchronised. Synchronisation can be performed via either wireless or wired connections. Wireless connections do not require a connecting infrastructure, so they are simpler. Wherever possible, it is preferable to use wired connections, which, in return for the cost of installing the network, allow for greater measurement accuracy.

UWB applications/h2>

UWB technology is spreading in the field of mobile devices, industry and the smart car sector.

In the iPhone world

Some vendors, including Apple, have already equipped their smartphones with UWB chips: inside the iPhone 11 there is already a UWB chip called U1.

The first applications to use the U1 chip allow the spatial location of devices. In this way it is possible to detect and locate all devices equipped with the chip within one’s own area. Until now this function has been carried out through the use of Bluetooth technology. The limitation of Bluetooth technology is that it only allows detection of the proximity of devices, but not positioning them in space as is possible with UWB systems.

It will thus be possible for Apple users to create a personal domain including their own devices (iPad, iWatch, iMac and Apple TV) and automatically synchronise with each other or exchange files on a spatial basis or even create scenarios in IoT and home automation.

From September, “AirDrop” will also use UWB to transfer files from one iPhone to another. Through U1 the presence of another similar smartphone is immediately detected and the data exchange becomes very fast and accurate.

Rumors about a new Apple device are circulating on the net: AirTags . An AirTag will be a small device equipped with a battery that can be associated with common objects in order to track or trace the associated object in case of theft or loss.

In the Android world

The next smartphones in the Android world will also take advantage of UWB technology. According to analysts at Barclays, in the coming months the first Android smartphones equipped with a new Ultra-Wideband, NFC and Secure Element “all-in-one” chip made by the Dutch company NXP Semiconductors will also be on the market.

NXP’s product will enable accurate and secure location, giving smartphones the ability to provide LBS services.

Manufacturers, led by Sony and Samsung together with NXP, are part of the FiRa (Fine Ranging) consortium. The mission of the consortium is the development and widespread adoption of user experiences that take advantage of the guaranteed accurate positioning capabilities of Ultra-Wideband (UWB) interoperable technologies.

NXP itself is part of a second consortium: CCC. The Car Connectivity Consortium® (CCC) is a cross-sector organisation that promotes global technologies for smartphone/car connectivity solutions. CCC is developing Digital Key, a new open standard to allow smart devices, such as smartphones, to act as vehicle keys. The Digital Key will allow drivers to lock and unlock their cars and even start the engine, and share access with others using smartphones. Another project, called Car Data, involves the creation of an ecosystem to enable a new set of services, such as pay-how-you-drive insurance, road monitoring and fleet management.

Also in the automotive sector, BMW is integrating UWB into its car systems. The idea is to integrate its CarKey on both iPhone and Apple Watch.

In the retail world

There will also be new applications in the retail world. Ultra-Wideband will replace Bluetooth in the location of devices (mostly smartphones) inside closed environments such as shops. The main purpose is to carry out proximity marketing and to have analytics to improve the management of the store. In this type of application, Ultra-Wideband will replace Bluetooth, providing (through the installation of a number of Anchors) the position and precise real-time movements of smartphones (associated with customers) within the store. The use of UWB technology will make it possible to send notifications and offers of certain products in real time and, of course, to collect data.

Conclusions

Nexsoft always has a keen eye for new technologies and applications. New technologies such as UWB are used in the context of research projects. In this way, in addition to experimenting and deploying an innovative product, we acquire new skills in the technological field.


If you want to know more about the type of IT projects we develop for our corporate clients, take a look at our dedicated web pages!

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